AAO2 impairment enhances aldehyde detoxification by AAO3 in Arabidopsis leaves exposed to UV-C or Rose-Bengal.

Among the three active aldehyde oxidases in Arabidopsis thaliana leaves (AAO1-3), AAO3, which catalyzes the oxidation of abscisic-aldehyde to abscisic-acid, was shown recently to function as a reactive aldehyde detoxifier. Notably, aao2KO mutants exhibited less senescence symptoms and lower aldehyde accumulation, such as acrolein, benzaldehyde, and 4-hydroxyl-2-nonenal (HNE) than in wild-type leaves exposed to UV-C or Rose-Bengal. The effect of AAO2 expression absence on aldehyde detoxification by AAO3 and/or AAO1 was studied by comparing the response of wild-type plants to the response of single-functioning aao1 mutant (aao1S), aao2KO mutants, and single-functioning aao3 mutants (aao3Ss). Notably, aao3Ss exhibited similar aldehyde accumulation and chlorophyll content to aao2KO treated with UV-C or Rose-Bengal. In contrast, wild-type and aao1S exhibited higher aldehyde accumulation that resulted in lower remaining chlorophyll than in aao2KO leaves, indicating that the absence of active AAO2 enhanced AAO3 detoxification activity in aao2KO mutants. In support of this notion, employing abscisic-aldehyde as a specific substrate marker for AAO3 activity revealed enhanced AAO3 activity in aao2KO and aao3Ss leaves compared to wild-type treated with UV-C or Rose-Bengal. The similar abscisic-acid level accumulated in leaves of unstressed or stressed genotypes indicates that aldehyde detoxification by AAO3 is the cause for better stress resistance in aao2KO mutants. Employing the sulfuration process (known to activate aldehyde oxidases) in wild-type, aao2KO, and molybdenum-cofactor sulfurase (aba3-1) mutant plants revealed that the active AAO2 in WT employs sulfuration processes essential for AAO3 activity level, resulting in the lower AAO3 activity in WT than AAO3 activity in aao2KO.

Ultraviolet C inactivation of Coxiella burnetii for production of a structurally preserved whole cell vaccine antigen.

Q fever, a worldwide-occurring zoonotic disease, can cause economic losses for public and veterinary health systems. Vaccines are not yet available worldwide and currently under development. In this regard, it is important to produce a whole cell antigen, with preserved structural and antigenic properties and free of chemical modifications. Thus, inactivation of Coxiella burnetii with ultraviolet light C (UVC) was evaluated. C. burnetii Nine Mile phase I (NMI) and phase II (NMII) were exposed to decreasing intensities in a time-dependent manner and viability was tested by rescue cultivation in axenic medium or cell culture. Effects on the cell structure were visualized by transmission electron microscopy and antigenicity of UVC-treated NMI was studied by immunization of rabbits. NMI and NMII were inactivated at UVC intensities of 250 µW/cm2 for 5 min or 100 µW/cm2 for 20 min. Reactivation by DNA repair was considered to be unlikely. No morphological changes were observed directly after UVC inactivation by transmission electron microscopy, but severe swelling and membrane degradation of bacteria with increasing severity occurred after 24 and 48 h. Immunization of rabbits resulted in a pronounced antibody response. UVC inactivation of C. burnetii resulted in a structural preserved, safe whole cell antigen and might be useful as antigen for diagnostic purposes or as vaccine candidate.

Dose-dependent inactivation of Plasmodium falciparum in red blood cell concentrates by treatment with short-wavelength ultraviolet light.

BACKGROUND AND OBJECTIVES: Plasmodium species are naturally transmitted by Anopheles mosquitos. The parasite infects red blood cells (RBCs) and can be transfused with blood products. In non-endemic areas, the main risk of infection arises from travellers coming back and people immigrating from malaria-endemic regions. Endemic countries face a permanent risk of infection from transfusion-transmitted malaria (TTM). TTM may cause life-threatening complications in patients dependent on blood donations. This study aimed to investigate the efficacy of Plasmodium falciparum inactivation in RBC units by treatment with short-wavelength ultraviolet C (UVC) light in the absence of photochemical additives. MATERIALS AND METHODS: RBC units were spiked with P. falciparum to a parasite density of 0.1%-1% and irradiated with up to 4.5 J/cm2 UVC. The parasite density of UVC-treated dilution series and untreated controls were compared over 3 weeks after irradiation. RESULTS: The lowest dose of 1.5 J/cm2 UVC led to a 3.1 log reduction in parasite load compared with the untreated control. The inactivation capacity was dose-dependent. Strikingly, 4.5 J/cm2 led to ≥5.3 log unit reduction, which was equivalent to a complete inactivation in two out of three experiments. CONCLUSION: Pathogen reduction with UVC light was previously shown to be effective for different bacteria and viruses, but the inactivation of parasites in RBC concentrates was not addressed until now. The present study provides evidence for significant inactivation of P. falciparum-infected RBCs by UVC light.

Externally supplied ascorbic acid moderates detrimental effects of UV-C exposure in cyanobacteria.

The defensive role performed by exogenously supplied ascorbic acid in the cyanobacterium Nostoc muscorum Meg1 against damages produced by UV-C radiation exposure was assessed in this study. Exposure to UV-C (24 mJ/cm2) significantly enhanced reactive oxygen species (ROS) (50%) along with peroxidation of lipids (21%) and protein oxidation (22%) in the organism. But, addition of 0.5 mM ascorbic acid prior to UV-C exposure showed reduction in ROS production (1.7%) and damages to lipids and proteins (1.5 and 2%, respectively). Light and transmission electron microscopic studies revealed that ascorbic acid not only protected filament breakage but also restricted severe ultrastructural changes and cellular damages in the organism. Although the growth of the organism was repressed up to 9% under UV-C treatment within 15 days, a pre-treatment with ascorbic acid led to growth enhancement by 42% in the same period. Various growth parameters such as photo-absorbing pigments (phycoerythrin, phycocyanin, allophycocyanin, chlorophyll a, and carotenoids), water splitting complex (WSC), D1 protein, RuBisCO, glutamine synthetase and nitrogenase activities in the UV-C treated organism were seen to be relatively intact in the presence of ascorbic acid. Thus, a detailed analysis undertaken in the present study was able to demonstrate that ascorbic acid not only act as first responder against harmful UV-C radiation by down-regulating ROS production, it also accelerated the growth performance in the organism in the post UV-C incubation period as an immediate response to an adverse experience presented in the form of UV-C radiation exposure.

Far-UVC Photolysis of Peroxydisulfate for Micropollutant Degradation in Water.

Increasing radical yields to reduce UV fluence requirement for achieving targeted removal of micropollutants in water would make UV-based advanced oxidation processes (AOPs) less energy demanding in the context of United Nations' Sustainable Development Goals and carbon neutrality. We herein demonstrate that, by switching the UV radiation source from conventional low-pressure UV at 254 nm (UV254) to emerging Far-UVC at 222 nm (UV222), the fluence-based concentration of HO• in the UV/peroxydisulfate (UV/PDS) AOP increases by 6.40, 2.89, and 6.00 times in deionized water, tap water, and surface water, respectively, with increases in the fluence-based concentration of SO4•- also by 5.06, 5.81, and 55.47 times, respectively. The enhancement to radical generation is confirmed using a kinetic model. The pseudo-first-order degradation rate constants of 16 micropollutants by the UV222/PDS AOP in surface water are predicted to be 1.94-13.71 times higher than those by the UV254/PDS AOP. Among the tested water matrix components, chloride and nitrate decrease SO4•- but increase HO• concentration in the UV222/PDS AOP. Compared to the UV254/PDS AOP, the UV222/PDS AOP decreases the formation potentials of carbonaceous disinfection byproducts (DBPs) but increases the formation potentials of nitrogenous DBPs.

Control of Aromatic Disinfection Byproducts in Potable Reuse Water by the UV222/H2O2 vs UV254/H2O2 Advanced Oxidation Processes.

Research has demonstrated the difficulty associated with degrading the conventional 1-2 carbon aliphatic halogenated byproducts of disinfectant reactions with organic matter [disinfection byproducts (DBPs)] within advanced oxidation process (AOP) units in potable reuse trains, but the efficacy of AOP units for treating the emerging classes of halogenated aromatic DBPs is unclear. We herein demonstrate more effective removal of 28 halogenated aromatic DBPs in the UV/H2O2 AOP at 222 nm (UV222) than in the conventional UV/H2O2 AOP at 254 nm. Direct photolysis of 28 halogenated aromatic DBPs was greatly enhanced at 222 nm with fluence-based photodecay rate constants of 4.31 × 10-4-1.53 × 10-2 cm2 mJ-1, which was mainly attributed to the higher molar absorption coefficients of halogenated aromatic DBPs at 222 nm than 254 nm. Generally, quantum yields of halogenated aromatic DBPs at both 222 and 254 nm followed the order of halophenols > halohydroxybenzaldehydes > halonitrophenols. All 28 halogenated aromatic DBPs exhibit high reactivity toward HO• with second-order rate constants ranging from 2.18 × 109 to 1.15 × 1010 M-1 s-1 determined by X-ray radiolysis. The UV fluence required to achieve 90% loss of halogenated aromatic DBPs in the UV222/H2O2 AOP was 75-95% lower than that in the UV254/H2O2 AOP, and 90% removal of most tested halogenated aromatic DBPs can be achieved in the UV222/H2O2 AOP within the UV fluence levels commonly applied in potable reuse (700-1000 mJ cm-2).

Far-UVC 222 nm Treatment: Effects of Nitrate/Nitrite on Disinfection Byproduct Formation Potential.

Irradiation at far ultraviolet C (far-UVC) 222 nm by krypton chloride (KrCl*) excilamps can enhance microbial disinfection and micropollutant photolysis/oxidation. However, nitrate/nitrite, which absorbs strongly at 222 nm, may affect the formation of disinfection byproducts (DBPs). Herein, we evaluated model organic matter and real water samples and observed a substantial increase in the formation potential for trichloronitromethane (chloropicrin) (TCNM-FP), a nitrogenous DBP, by nitrate or nitrite after irradiation at 222 nm. At a disinfection dose of 100 mJ·cm-2, TCNM-FP of humic acids and fulvic acids increased from ∼0.4 to 25 and 43 µg·L-1, respectively, by the presence of 10 mg-N·L-1 nitrate. For the effect of nitrate concentration, the TCNM-FP peak was observed at 5-10 mg-N·L-1. Stronger fluence caused a greater increase of TCNM-FP. Similarly, the increase of TCNM-FP was also observed for wastewater and drinking water samples containing nitrate. Pretreatment using ozonation and coagulation, flocculation, and filtration or the addition of H2O2 can effectively control TCNM-FP. The formation potential of other DBPs was minorly affected by irradiation at 222 nm regardless of whether nitrate/nitrite was present. Overall, far-UVC 222 nm treatment poses the risk of increasing TCNM-FP of waters containing nitrate or nitrite at environmentally relevant concentrations and the mitigation strategies merit further research.

Cell density and extracellular matrix composition mitigate bacterial biofilm sensitivity to UV-C LED irradiation.

Ultraviolet-C light-emitting diodes (UV-C LEDs) are an emerging technology for decontamination applications in different sectors. In this study, the inactivation of bacterial biofilms was investigated by applying an UV-C LED emitting at 280 nm and by measuring both the influence of the initial cell density (load) and presence of an extracellular matrix (biofilm). Two bacterial strains exposing diverging matrix structures and biochemical compositions were used: Pseudomonas aeruginosa and Leuconostoc citreum. UV-C LED irradiation was applied at three UV doses (171 to 684 mJ/cm2) on both surface-spread cells and on 24-h biofilms and under controlled cell loads, and bacterial survival was determined. All surface-spread bacteria, between 105 and 109 CFU/cm2, and biofilms at 108 CFU/cm2 showed that bacterial response to irradiation was dose-dependent. The treatment efficacy decreased significantly for L. citreum surface-spread cells when the initial cell load was high, while no load effect was observed for P. aeruginosa. Inactivation was also reduced when bacteria were grown under a biofilm form, especially for P. aeruginosa: a protective effect could be attributed to abundant extracellular DNA and proteins in the matrix of P. aeruginosa biofilms, as revealed by Confocal Laser Scanning Microscopy observations. This study showed that initial cell load and exopolymeric substances are major factors influencing UV-C LED antibiofilm treatment efficacy. KEY POINTS: • Bacterial cell load (CFU/cm2) could impact UV-C LED irradiation efficiency • Characteristics of the biofilm matrix have a paramount importance on inactivation • The dose to be applied can be predicted based on biofilm properties.

Milk microbiome transplantation: recolonizing donor milk with mother's own milk microbiota.

Donor human milk (DHM) provides myriad nutritional and immunological benefits for preterm and low birthweight infants. However, pasteurization leaves DHM devoid of potentially beneficial milk microbiota. In the present study, we performed milk microbiome transplantation from freshly collected mother's own milk (MOM) into pasteurized DHM. Small volumes of MOM (5%, 10%, or 30% v/v) were inoculated into pasteurized DHM and incubated at 37 °C for up to 8 h. Further, we compared microbiome recolonization in UV-C-treated and Holder-pasteurized DHM, as UV-C treatment has been shown to conserve important biochemical components of DHM that are lost during Holder pasteurization. Bacterial culture and viability-coupled metataxonomic sequencing were employed to assess the effectiveness of milk microbiome transplantation. Growth of transplanted MOM bacteria occurred rapidly in recolonized DHM samples; however, a greater level of growth was observed in Holder-pasteurized DHM compared to UV-C-treated DHM, potentially due to the conserved antimicrobial properties in UV-C-treated DHM. Viability-coupled metataxonomic analysis demonstrated similarity between recolonized DHM samples and fresh MOM samples, suggesting that the milk microbiome can be successfully transplanted into pasteurized DHM. These results highlight the potential of MOM microbiota transplantation to restore the microbial composition of UV-C-treated and Holder-pasteurized DHM and enhance the nutritional and immunological benefits of DHM for preterm and vulnerable infants. KEY POINTS: • Mother's own milk microbiome can be successfully transplanted into donor human milk. • Recolonization is equally successful in UV-C-treated and Holder-pasteurized milk. • Recolonization time should be restricted due to rapid bacterial growth.

Comparing resistance of bacterial spores and fungal conidia to pulsed light and UVC radiation at a wavelength of 254 nm.

Pulsed light (PL) inactivates microorganisms by UV-rich, high-irradiance and short time pulses (250 µs) of white light with wavelengths from 200 nm to 1100 nm. PL is applied for disinfection of food packaging material and food-contact equipment. Spores of seven Bacillus ssp. strains and one Geobacillus stearothermophilus strain and conidia of filamentous fungi (One strain of Aspergillus brasiliensis, A. carbonarius and Penicillium rubens) were submitted to PL (fluence from 0.23 J/cm2 to 4.0 J/cm2) and UVC (at λ = 254 nm; fluence from 0.01 J/cm2 to 3.0 J/cm2). One PL flash at 3 J/cm2 allowed at least 3 log-reduction of all tested microorganisms. The emetic B. cereus strain F4810/72 was the most resistant of the tested spore-forming bacteria. The PL fluence to 3 log-reduction (F3 PL) of its spores suspended in water was 2.9 J/cm2 and F3 UVC was 0.21 J/cm2, higher than F3 PL and F3 UVC of spores of B. pumilus SAFR-032 2.0 J/cm2 and 0.15 J/cm2, respectively), yet reported as a highly UV-resistant spore-forming bacterium. PL and UVC sensitivity of bacterial spores was correlated. Aspergillus spp. conidia suspended in water were poorly sensitive to PL. In contrast, PL inactivated Aspergillus spp. conidia spread on a dry surface more efficiently than UVC. The F2 PL of A. brasiliensis DSM1988 was 0.39 J/cm2 and F2 UVC was 0.83 J/cm2. The resistance of spore-forming bacteria to PL could be reasonably predicted from the knowledge of their UVC resistance. In contrast, the sensitivity of fungal conidia to PL must be specifically explored.

Comprehensive phytochemical analysis of Salvia hispanica L. callus extracts using LC-MS/MS.

In this research, the study utilized the root, leaf, and petiole parts of in vitro grown Salvia hispanica plants as explants. Following UV-C treatment applied to developing callus, methanol extracts were obtained and analyzed using liquid chromatography-mass spectrometry (LC/MS) to investigate their anticancer properties. First, the seeds of S. hispanica were soaked in commercial bleach for 6 min to ensure surface sterilization. The most effective antimicrobial activity on Gram-negative bacteria, with a zone diameter (11 ± 0.82 mm), was noticed in callus extracts obtained from the petiole explant in the second protocol against Klebsiella pneumoniae EMCS bacteria. Anticancer activities on SH-SY5Y human neuroblastoma cells were investigated by using 1000, 500, 250, 125, 62.5, 31.25, 15.62, and 78.12 µg/mL doses of the extracts, and the most effective cytotoxic activity was determined at the 1000 µg/mL dose of the extracts obtained from both protocols. The extracts were determined to inhibit hCAI, hCAII, AChE, and BChE enzymes. The content of 53 different phytochemical components of the extracts was analyzed by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Rosmarinic acid, quinic acid, and caffeic acid were found in the highest concentration. The comprehensive LC-MS/MS analysis of S. hispanica extracts revealed a diverse array of phytochemical compounds, highlighting its potential for therapeutic applications.

Development of porcine embryos cultured in media irradiated with ultraviolet-C.

Sterilization of the culture medium using ultraviolet (UV)-C reduces the potential adverse effects of microorganisms and allows for long-term use. In the present study, we investigated the effects of a medium directly irradiated with UV-C prior to in vitro culture on the development and quality of porcine in vitro-fertilized embryos and the free amino acid composition of the culture media. The culture media (porcine zygote medium [PZM-5] and porcine blastocyst medium [PBM]) were irradiated with UV-C at 228 and 260 nm for 1 and 3 days, respectively. Next, the culture media were irradiated with UV-C at 228 nm for 3, 7, or 14 days. After in vitro fertilization, the embryos were cultured in the UV-C-irradiated media for 7 days. Free amino acid levels in culture media irradiated with 228 and 260 nm UV-C for 3 days were analysed. The blastocyst formation rate of embryos cultured in media irradiated with 260 nm UV-C for 3 days was significantly lower than that of embryos cultured in non-irradiated control media. However, 228 nm UV-C irradiation for up to 14 days did not affect blastocyst formation rates and quality in the resulting blastocysts. Moreover, 260 nm UV-C irradiation significantly increased the taurine concentration in both culture media and decreased methionine concentration in the PBM. In conclusion, UV-C irradiation at 228 nm before in vitro culture had no detrimental effects on embryonic development. However, 260 nm UV-C irradiation decreased embryo development and altered the composition of free amino acids in the medium.

Nighttime Applications of Germicidal UV Light to Suppress Cercospora Leaf Spot in Table Beet.

Cercospora leaf spot (CLS), caused by the hemibiotrophic fungus Cercospora beticola, is a destructive disease affecting table beet. Multiple applications of fungicides are needed to reduce epidemic progress to maintain foliar health and enable mechanized harvest. The sustainability of CLS control is threatened by the rapid development of fungicide resistance, the need to grow commercially acceptable yet CLS-susceptible cultivars, and the inability to manipulate agronomic conditions to mitigate disease risk. Nighttime applications of germicidal UV light (UV-C) have recently been used to suppress several plant diseases, notably those caused by ectoparasitic biotrophs such as powdery mildews. We evaluated the efficacy of nighttime applications of UV-C for suppression of CLS in table beet. In vitro lethality of UV-C to germinating conidia increased with increasing dose, with complete suppression at 1,000 J/m2. Greenhouse-grown table beet tolerated relatively high doses of UV-C without lethal effects despite some bronzing on the leaf blade. A UV-C dose >1,500 J/m2 resulted in phytotoxicity severities greater than 50%. UV-C exposure to ≤750 J/m2 resulted in negligible phytotoxicity. Older (6-week-old) greenhouse-grown plants were more susceptible to UV-C damage than younger (2- and 4-week-old) plants. Suppression of CLS by UV-C was greater when applied within 6 days of C. beticola inoculation than if delayed until 13 days after infection in greenhouse-grown plants. In field trials, there were significant linear relationships between UV-C dose and CLS control and phytotoxicity severity, and a significant negative linear relationship between phytotoxicity and CLS severity at the final assessment. Significant differences between UV-C doses on the severity of CLS and phytotoxicity indicated an efficacious dose near 800 J/m2. Collectively, these findings illustrate significant and substantial suppression by nighttime applications of UV-C for CLS control on table beet, with potential for incorporation in both conventional and organic table beet broadacre production systems.

Can Extraintestinal Pathogenic Escherichia coli with Heat Resistance Profile Overcome Nonthermal Technologies?

Ultraviolet-C light-emitting diode (UVC-LED) and ultrasound (US) are two nonthermal technologies with the potential to destroy pathogens. However, little is known about their effectiveness in strains with a history of heat resistance. Thus, this study aimed to evaluate the phenotype and genotype of heat-resistant extraintestinal pathogenic Escherichia coli (ExPEC) with heat resistance genes after the application of US, UVC-LED, and UVC-LED+US. For this, two central composite rotatable designs were used to optimize the UVC-LED and US conditions in four ExPEC isolated from beef. From the genome of these isolates obtained in a previous study, possible genes for UVC resistance were analyzed. Results showed that US was ineffective in reducing >0.30 log colony-forming unit/mL, and that when used after UVC-LED, it showed a nonsynergic or antagonistic effect. Also, UVC-LED had the greatest effect at the maximum dose (4950 mJ/cm2 from 1.65 mW/cm2 for 50 min). However, the strains showed some recovery after that, which could be implicated in the expression of genes included in SOS system genes, some others present in the transmissible Locus of Stress Tolerance (trxBC and degP), and others (terC). Thus, ExPEC can overcome the conditions used in this study for US, UVC-LED, and UVC-LED+US, probably due to the history of resistance to other cellular damage. The result of this study will contribute to future studies that aim to find better treatment conditions for each food product.

Novel treatment of infectious keratitis in canine corneas using ultraviolet C (UV-C) light.

OBJECTIVE: To investigate the therapeutic effect of 275 nm wavelength ultraviolet C (UV-C) light for treatment of bacterial keratitis in canine corneas using an affordable, broadly available modified handheld device. METHODS: UV-C therapy (UVCT) was evaluated in two experiments: in vitro using triplicates of three bacterial genera (Staphylococcus, Streptococcus, Pseudomonas spp., and a mix of all species) where the UVCT was performed at a distance of 10, 15, and 20 mm with 1 or 2 doses (4 h apart) for 5, 15, or 30 s; ex vivo model where healthy canine corneal buttons were inoculated superficially and deep (330 µm) with the same bacterial isolates and treated at a 10 mm distance for 15 s with one dose of 22.5 mJ/cm2. Fluorescent marker (STYO9-PI) was used to label (green = live bacteria, red = dead bacteria), and confocal microscopy was used to image the bacteria. RESULTS: In vitro results showed all plates treated with UVCT had 100% bactericidal effect for all isolates with single dose of 15 s at 10 mm distance or two doses, 4 h apart at 15 mm and was ineffective with single dose at 15-20 mm. The ex vivo results confirmed a significant decrease in bacterial load for all isolates on samples inoculated superficially but were inconclusive for intrastromal ones. CONCLUSIONS: UVCT confirmed the therapeutic potential for all tested isolates, for both in vitro and ex vivo experiments using a single exposure of 15 s. While safety studies are underway, clinical trials are warranted.

Quantification of UV Light-Induced Spectral Response Degradation of CMOS-Based Photodetectors.

High-energy radiation is known to potentially impact the optical performance of silicon-based sensors adversely. Nevertheless, a proper characterization and quantification of possible spectral response degradation effects due to UV stress is technically challenging. On one hand, typical illumination methods via UV lamps provide a poorly defined energy spectrum. On the other hand, a standardized measurement methodology is also missing. This work provides an approach where well-defined energy spectrum UV stress conditions are guaranteed via a customized optical set up, including a laser driven light source, a monochromator, and a non-solarizing optical fiber. The test methodology proposed here allows performing a controlled UV stress between 200 nm and 400 nm with well-defined energy conditions and offers a quantitative overview of the impact on the optical performance in CMOS-based photodiodes, along a wavelength range from 200 to 1100 nm and 1 nm step. This is of great importance for the characterization and development of new sensors with a high and stable UV spectral response, as well as for implementation of practical applications such as UV light sensing and UV-based sterilization.

Coverage Planning for UVC Irradiation: Robot Surface Disinfection Based on Swarm Intelligence Algorithm.

Ultraviolet (UV) radiation has been widely utilized as a disinfection strategy to effectively eliminate various pathogens. The disinfection task achieves complete coverage of object surfaces by planning the motion trajectory of autonomous mobile robots and the UVC irradiation strategy. This introduces an additional layer of complexity to path planning, as every point on the surface of the object must receive a certain dose of irradiation. Nevertheless, the considerable dosage required for virus inactivation often leads to substantial energy consumption and dose redundancy in disinfection tasks, presenting challenges for the implementation of robots in large-scale environments. Optimizing energy consumption of light sources has become a primary concern in disinfection planning, particularly in large-scale settings. Addressing the inefficiencies associated with dosage redundancy, this study proposes a dose coverage planning framework, utilizing MOPSO to solve the multi-objective optimization model for planning UVC dose coverage. Diverging from conventional path planning methodologies, our approach prioritizes the intrinsic characteristics of dose accumulation, integrating a UVC light efficiency factor to mitigate dose redundancy with the aim of reducing energy expenditure and enhancing the efficiency of robotic disinfection. Empirical trials conducted with autonomous disinfecting robots in real-world settings have corroborated the efficacy of this model in deactivating viruses.

RoboCoV Cleaner: An Indoor Autonomous UV-C Disinfection Robot with Advanced Dual-Safety Systems.

In the face of today's ever-evolving global health landscape and ambient assisted living (AAL), marked by the persistent emergence of novel viruses and diseases that impact vulnerable categories and individual safety, the need for innovative disinfection solutions has surged to unprecedented levels. In pursuit of advancing the field of autonomous UV-C disinfection robotics, we conducted two comprehensive state-of-the-art analyses: the first one in the literature and the second one in existing commercial disinfection robots to identify current challenges. Of all of the challenges, we consider the most outstanding ones to be safeguarding humans and animals and understanding the surroundings while operating the disinfection process challenges that we will address in this article. While UV-C lamps have demonstrated their effectiveness in sterilizing air and surfaces, the field of autonomous UV-C disinfection robotics represents a critical domain that requires advancement, particularly in safeguarding the wellbeing of humans and animals during operation. Operating UV-C disinfection robots in close proximity to humans or animals introduces inherent risks, and existing disinfection robots often fall short in incorporating advanced safety systems. In response to these challenges, we propose the RoboCoV Cleaner-an indoor autonomous UV-C disinfection robot equipped with an advanced dual and redundant safety system. This novel approach incorporates multiple passive infrared (PIR) sensors and AI object detection on a 360-degree camera. Under our test, the dual-redundant system reached more than 90% when detecting humans with high accuracy using the AI system 99% up to 30 m away in a university hallway (different light conditions) combined with the PIR system (with lower accuracy). The PIR system was proved to be a redundant system for uninterrupted operation during communication challenges, ensuring continuous sensor information collection with a swift response time of 50 ms (image processing within 200 ms). It empowers the robot to detect and react to human presence, even under challenging conditions, such as when individuals wear masks, in complete darkness, under UV light, or in environments with blurred visual conditions. In our test, the detection system performed outstandingly well with up to 99% detection rate of humans. Beyond safety features, the RoboCoV Cleaner can identify objects in its surroundings. This capability empowers the robot to discern objects affected by UV-C light, enabling it to apply specialized rules for targeted disinfection. The proposed system exhibits a wide range of capabilities beyond its core purpose of disinfection, making it suitable for healthcare facilities, universities, conference venues, and hospitals. Its implementation has the ability to improve significantly human safety and protect people. By showcasing the RoboCoV Cleaner's safety-first approach and adaptability, we aim to set a new benchmark for UV-C disinfection robots, promoting clean and secure environments while protecting vulnerable people, even in challenging scenarios.

Performance of high-efficiency UV-C LEDs in water disinfection: Experimental, life cycle assessment, and economic analysis of different operational scenarios.

The widespread use of low or medium pressure mercury lamps in UV-C water disinfection should consider recent advances in UV-C LED lamps that offer a more sustainable approach and avoid its main drawbacks. The type of water and the mode of operation are critical when deciding on the treatment technology to be used. Therefore, this study investigates the potential application of UV-C LED disinfection technology in terms of kinetics, environmental assessment, and economic analysis for two scenarios: the continuous disinfection of a wastewater treatment plant (WWTP), and disinfection of harvested rainwater (RWH) in a residential household that operates intermittently. Experiments are conducted using both the new UV-C LED system and the conventional mercury lamp to disinfect real wastewater. Removal of total coliforms and Escherichia coli bacteria, with concentrations of approximately 105 and 104 CFU per 100 mL has been followed to assess the performance of both types of UV-C lamps. The experimental study provides kinetic parameters that have been further used in the environmental assessment conducted from a life cycle perspective. Additionally, considering the significant role of electricity consumption, a preliminary economic analysis has been conducted. The results indicate that first-order kinetic constants of pathogens removal with UV-C LEDs achieve 1.4 times higher values than Hg lamp. Regarding the environmental and economic assessment, for disinfection systems operating continuously, LEDs result in environmental impacts 5 times higher than Hg lamp in most categories, indicating that Hg lamps offer a viable option both from economic and environmental point of view. However, for installations with intermittent operation, LEDs emerge as the most competitive alternative, due to their ability to be turned on and off without affecting their lifespan. This study shows that UV-C LED lamps hold promise to replace conventional mercury lamps in a near future.

UVC Stokes and Anti-Stokes Emission of Ca9Y(PO4)7 Polycrystals Doped with Pr3+ Ions.

The recent COVID-19 pandemic has made everyone aware of the threat of viruses and the growing number of antibiotic-resistant bacteria. It has become necessary to find new methods to combat these hazards. One tool that could be used is UVC radiation, i.e., 100-280 nm. Currently, the available sources of this light are mercury vapor lamps. However, the modern world requires more compact, mercury-free, and less energy-consuming light sources. This work presents the results of our research on a new material in which efficient UVC radiation was obtained. Here, we present the results of research on Ca9Y(PO4)7 polycrystals doped with Pr3+ ions prepared using the solid-state method. The absorption, excitation, emission, and emission decay profiles of praseodymium(III) ions were measured and analyzed. The upconversion emission in the UVC region excited by blue light was observed. Parameters such as energy bandgap, refractive index, and thermal stability of luminescence were determined. The studied phosphate-based phosphor possesses promising characteristics that show its potential in luminescent applications in future use in medicine or for surface disinfection.